Cardiorespiratory fitness. Fitness will be evaluated at Baseline (second run-in/assessment session) and at 6- and 12-month follow-up with a maximal treadmill test (see Core C). The Baseline symptom-limited maximum stress test represents the current standard of care for an exercise prescription. The primary measure for assessing change will be change in maximal oxygen uptake (VO2 max). Heart rate, ECG changes, blood pressure and VO2 max will be determined during the exercise test. For the maximum exercise stress tests the participant will be continued on any prescribed medication for cardiovascular disease. The following 3 abnormalities classify an individual at moderate to high risk for cardiac complication during exercise and will result in study exclusion: 1) 2 or more previous myocardial infarctions; (2) previous episode of primary cardiac arrest; (3) exercise capacity < 6 METS, (4) ischemic horizontal or downsloping ST segment depression ≥ 4.0 mm, or (5) angina during exercise (see Core C for details).